Mannion decided to return for his senior season, solidifying that position for the Beavers. Luke Del Rio, Brent VanderVeen and Kyle Kempt will compete as his backup during camp, which opens for Oregon State on Monday.

In a conference call with reporters on Thursday afternoon to preview camp, Riley said his chief concerns were Oregon State's offensive line and the cornerback position.

The line loses three starters from last season, Grant Enger, Josh Andrews and Michael Phillip.

Center Isaac Seumalo, who will likely shift positions this season, is still recovering from a broken foot he sustained during the Hawaii Bowl. It is not known if he will be able to come back in time for the Beavers' opener at home against Portland State on Aug. 30.

Fellow lineman Josh Mitchell was coming off of shoulder surgery and Grant Bays has had back issues that slowed him during spring practice.

A solid offensive line is key not only to Mannion's protection but also to Oregon State's running game, which struggled last season before showing some spark in the Civil War against Oregon and in the victory over the Broncos. The Beavers bring back Terron Ward and Storm Woods, who combined for 998 yards and 11 touchdowns last year.

"We're going to have to continue to formulate that line through camp and solidify it," Riley said. "If we can get everyone healthy and working well together that will certainly be a good sign for our running attack."

Riley said he is also concerned about the cornerback position and who will play opposite Steven Nelson now that Rashaad Reynolds has moved on to the NFL. The Beavers' coach would also like to nail down the defensive front following the loss of Scott Crichton.

He also said he plans to add live scrimmages during fall camp. Last year the team didn't hold any because of injuries.

"We want to make sure our players are prepared. So more intermittent live work with a couple of probably 50-play scrimmages involved in there would be what we're pointing toward," he said.

Oregon State was picked to finish fourth in the Pac-12 North this season by reporters who cover the league. Rival Oregon was picked to finish atop the division and win the conference title.

The Beavers on Thursday announced the addition of linebacker Kyle Haley, who had 56 tackles last season as a freshman at Golden West Community College in Huntington Beach, California.

Earlier this week Oregon State also announced five walk-ons: offensive lineman Mason Johnson, long snapper Connor Kelsey, fullback Iona Pritchard and wide receivers Drew Kell and Gabe Ovgard. All are true freshman except Pritchard, who is a post-graduate fifth-year senior from BYU.

Despite his concerns, Riley was ready to get the season going.

"This is a great time of year, but it's also sobering in some ways because you're entering the submarine for a series of months, and there will be a lot of things we go through in that time," he said.